<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .item {
      color: red;
    }

    .box:not(.why) {
      color: blue;
    }
  </style>
</head>

<body>
  <div class="box">
    <div class="item">列表内容1</div>
    <div class="item">列表内容2</div>
    <div class="why">列表内容3</div>
    <div class="item">列表内容4</div>
    <div class="item">列表内容5</div>
    <div>列表内容5</div>
    <div>列表内容5</div>
    <div>列表内容5</div>
    <div>列表内容5</div>
  </div>
</body>

</html>